The present invention relates to automobile suspensions and more particularly relates to a method and apparatus for aligning the rear axle of an automobile with respect to the frame.
A typical rear suspension system for automobiles currently in use includes two elongate lower control arms made of sheet metal stampings of box or channel cross section. The control arms have radial type rubber bushings installed at their ends. Each of the lower control arms is connected at a first end to a bracket on the automobile frame by means of a pin inserted through the rubber bushing and the bracket. The other end of each lower control arm is connected to a bracket on the lower side of the rear axle housing, one arm adjacent each rear wheel, also by means of a pin inserted through the bracket and bushing. Upper control arms of channel cross section, similar to but usually shorter than the lower control arms, also have radial bushings installed at their ends and are connected between the frame and the upper side of the rear axle by a pin and bracket arrangement similar to that used with the lower control arms. A coil spring is located near each of the rear wheels interposed between a seat on the frame and a pad on the top of the axle housing or on the top of the lower control arm.
The rear wheel suspensions constructed as described above have a number of shortcomings. For example, during manufacture the manufacturing tolerances in each of the rear suspension component parts can build up and result in displacement of the rear axle with respect to the frame thereby hindering proper rear wheel tracking. The mistracking of the rear wheels can cause steering instability resulting in poor driver control over the automobile. The improper tracking can also cause toe-in of the rear wheels, resulting in abnormally rapid tire wear.
At the present time, there is no easy method of correcting such misalignment of the rear wheels of the automobile. In order to correct the mistracking problem, it is sometimes necessary to take drastic structural modification steps, such as shortening the lower control arm. In the alternative, it may be possible to correct the tracking problem by replacing all of the bushings in the rear suspension system. The first alternative is time consuming and expensive and the second alternative is not always successful since it is possible to replace all of the bushings in the rear suspension and still have the tolerances build up so that the net result is a continuation of the rear axle alignment and mistracking problem. In fact, one major automobile manufacturer abandoned its use of coil spring rear suspension on passenger automobiles because it could not satisfactorily correct mistracking problems.
It is therefore an object of the present invention to provide a method and apparatus for aligning the rear suspension of an automobile.
It is a further object of this invention to provide such a method and apparatus that is relatively easy to install as a modification to existing equipment in order to transform a formerly unalignable rear axle housing into one which is readily adjustable.
It is another object of this invention to provide an apparatus for installation on the rear suspension of an automobile which allows the relationship of the lower control arm and the axle housing to be adjusted to thereby align the rear wheels.
It is a further object of this invention to provide such an adjustable connection that is structurally sound enough to withstand the torque and forces to which the rear suspension of an automobile is subjected during normal driving, but that is relatively inexpensive to construct and easy to install and maintain.